Component temperature control by coolant flow control and heater duty cycle control

ABSTRACT

Methods and systems for controlling temperatures in plasma processing chamber for a wide range of setpoint temperatures and reduced energy consumption. Temperature control is coordinated between a coolant liquid loop and a heat source by a control algorithm implemented by the plasma processing module controller. The control algorithm may completely stop the flow of coolant liquid to a temperature-controlled component in response to a feedback signal indicating an actual temperature is below the setpoint temperature. The control algorithm may further be based at least in part on a feedforward control signal derived from a plasma power or change in plasma power input into the processing chamber during process recipe execution.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. PROVISIONAL PATENTAPPLICATION No. 61/349,073 filed May 27, 2010, and entitled “COMPONENTTEMPERATURE CONTROL BY COOLANT FLOW CONTROL AND HEATER DUTY CYCLECONTROL,” incorporated herein by reference in its entirety for allpurposes.

BACKGROUND

1) Field

Embodiments of the present invention generally relate to plasmaprocessing equipment, and more particularly to methods of controllingtemperatures during processing of a workpiece with a plasma processingchamber.

2) Description of Related Art

In a plasma processing chamber, such as a plasma etch or plasmadeposition chamber, the temperature of a chamber component is often animportant parameter to control during a process. For example, atemperature of a substrate holder, commonly called a chuck or pedestal,may be controlled to heat/cool a workpiece to various controlledtemperatures during the process recipe (e.g., to control an etch rate).Similarly, a temperature of a showerhead/upper electrode or othercomponent may also be controlled during the process recipe to influencethe processing. Conventionally, a heat sink and/or heat source iscoupled to the processing chamber to control the temperature of achamber component at a setpoint temperature. Typically, a firstcontroller, such as a PID (proportional-integral-differential)controller is employed for feedback control of the heat transfer betweenthe temperature-controlled component and a heat sink while a secondcontroller is employed for feedback control of the heat transfer betweenthe temperature-controlled component and a heat source. Each of thefirst and second controllers generally operate in isolation of theother, independently executing their own closed loop control algorithms,in essence providing two control loops which counter balance each other.Typically, a cooling control loop based on a liquid coolant operateswith a nominal coolant liquid flow (e.g., ˜1 GPM) at all times for thecooling loop to stay at a controlled steady state. As such, coolantliquid in the coolant lines is not allowed to stagnate within thecoolant loop.

An effect of this conventional control configuration is that the controleffort of each control loop needs to be approximately the same toneutralize an external disturbance quickly, such as an input of wasteheat energy from a RF generator driving a plasma. When this externaldisturbance happens to be large, the control effort to neutralize thedisturbance must be made correspondingly large. For example, a heat sinkcontrol loop must provide a large sink by operating at a very lowtemperature and/or having a large thermal mass, etc. However, duringtimes when the external disturbances are much less, for example when aplasma processing system is in an idle state and there is no plasmapower input to the system, the cooling effect of the large heat sinkcannot be completely removed where a coolant loop maintains a nominalcoolant flow. Instead, even during such idle times, the cooling effectis actively countered by the second controller via application of asignificant amount of heating energy (e.g., 3000 W, or more) to maintainthe setpoint temperature. In addition to this inefficiency, anothereffect of the conventional control configuration is that the upper limitof the component temperature is limited by the activity of the largeheat sink. For example, even with application of 100% heating power, theeffect of the large heat sink limits the maximum component temperatureto a value less than what would be possible if the heat sink activitycould be further reduced. For a similar reason, the transient responseto increases in the setpoint temperature is also slow. The end result ofthe convention configuration is energy inefficient system operation withlimited processing temperature range and increased transient responsetimes.

SUMMARY

Methods and systems for controlling a process or chamber componenttemperature as a plasma process is executed by plasma processingapparatus are described herein. In certain embodiments, methods andsystems coordinate heat transfer between the process chamber and both aheat sink and a heat source. In a particular embodiment, methods andsystems coordinate coolant liquid flow control and heater duty cyclecontrol to reduce the amount of energy required to maintain a setpointtemperature in absence of an external disturbance while still achievinga fast control response to neutralize an external disturbance.

Certain embodiments include a method whereby a temperature in theprocess chamber is controlled at a chamber management level rather thanat the level of an individual heat sink or source. In furtherembodiments the chamber management level control is based, at least inpart, on a feedback signal indicating an error between the chambercomponent temperature and a setpoint temperature. When the componenttemperature is below the setpoint temperature, both a heating powerinput to heat the chamber component may be increase and a coolant liquidflow between the process chamber and a heat sink external to the processchamber may be reduced to a flow rate of zero in response to thefeedback signal.

In an embodiment, one or more of the coolant liquid flow and a heaterpower controlling the component temperature is further determined with afeedforward control signal based on a plasma power input to the processchamber when the chamber is in an active state executing a plasmaprocess recipe. In particular embodiments, a transfer function of aninput plasma power signal is to compensate a heating of the processchamber component by the plasma power output by the power source. Incertain such embodiments, the coolant liquid flow and the heating powercontrol includes applying a first group of gain values during a firstportion of an executing step in a plasma process recipe, the first groupof gain values associated with a plasma input power and the setpointtemperature for the executing recipe step. A second group of gain valuesmay further be applied during a second portion of the executing recipestep, the second group of gain values associated with a change in theplasma input power and a change in the setpoint temperature between theexecuting step and a preceding or subsequent plasma process recipe step.

Embodiments include a computer readable media storing instructions whichwhen executed by a processing system cause the processing system tocoordinate heat transfer between the process chamber and both a heatsink and a heat source. In one such embodiment, computer readable mediastores instructions to coordinate coolant liquid flow control and heaterduty cycle control to reduce the amount of energy required to maintain asetpoint temperature in absence of an external disturbance while stillachieving a fast control response to neutralize an external disturbance.In particular embodiments, the computer readable media includes atransfer function between the plasma power signal and the componenttemperature and further includes instructions to compensate a heating ofthe process chamber component by the plasma power output.

Embodiments include a plasma processing chamber, such as a plasma etchor plasma deposition system, having a temperature-controlled componentto be coupled to a heat sink/heat source. The temperature-controlledcomponent may be coupled to a heat sink by a coolant liquid loopincluding a coolant liquid control valve which completely stops thecoolant liquid flow to the temperature-controlled component. The chambermay further include a temperature controller coupled to the coolantliquid control valve to control a heat transfer between thetemperature-controlled component and the heat sink by varying thecoolant liquid flow rate over a range including zero liquid flow.

A plasma power source is to be coupled to the processing chamber toenergize a plasma during processing of a workpiece disposed in theprocess chamber. The temperature controller may coordinate control ofheat transfer between the temperature-controlled component and both aheat sink and a heat source by way of a feedback control signal and/or afeedforward control signal based on a plasma power input to the chamberto compensate a plasma heating of the temperature-controlled component.In one such embodiment, the temperature-controlled component comprises aprocess gas showerhead configured to deliver process gas during plasmaprocessing.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are particularly pointed out and distinctlyclaimed in the concluding portion of the specification. Embodiments ofthe invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings in which:

FIG. 1 is a block diagram illustrating a temperature control systemincluding both feedforward and feedback control elements and providing acoordinate control effort responsive to both heating and cooling, inaccordance with an embodiment of the present invention;

FIG. 2A illustrates a schematic of a plasma etch system including atemperature controller, in accordance with an embodiment of the presentinvention;

FIG. 2B illustrates a block diagram of a components in a temperaturecontrol chain, in accordance with an embodiment of the presentinvention;

FIG. 3A is a state diagram illustrating control loop configurations foran idle state and an active state of a plasma processing chamber, inaccordance with an embodiment of the present invention;

FIG. 3B is a block diagram illustrating particular segments in a plasmaprocessing recipe executed during active states before and after an idlestate, in accordance with an embodiment of the present invention

FIG. 3C is a flow diagram illustrating operations in a method for takingthe control system described in FIG. 1 offline, in accordance with anembodiment of the present invention;

FIG. 4A illustrates an event driven control algorithm for controlling acomponent temperature with the control system described in FIG. 1 duringan idle state, in accordance with an embodiment of the presentinvention;

FIG. 4B is a flow diagram illustrating operations in a method forcontrolling a component temperature with the control system described inFIG. 1 during an active state, in accordance with an embodiment of thepresent invention;

FIG. 4C illustrates a gain group lookup table, in accordance with anembodiment of the present invention;

FIG. 4D illustrates a control algorithm for addressing changes insetpoint temperatures between two steps in a plasma process recipe, inaccordance with an embodiment of the present invention;

FIG. 4E illustrates a lookup table for a gain group employed by thecontrol algorithm of FIG. 4D, in accordance with an embodiment of thepresent invention; and

FIG. 5 illustrates a block diagram of an exemplary computer systemincorporated into the plasma etch system depicted in FIG. 3, inaccordance with one embodiment of the present invention.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of embodiments of theinvention. However, it will be understood by those skilled in the artthat other embodiments may be practiced without these specific details.In other instances, well-known methods, procedures, components andcircuits have not been described in detail so as not to obscure thepresent invention. Some portions of the detailed description thatfollows are presented in terms of algorithms and symbolicrepresentations of operations on data bits or binary digital signalswithin a computer memory. These algorithmic descriptions andrepresentations may be the techniques used by those skilled in the dataprocessing arts to convey the substance of their work to others skilledin the art.

An algorithm or method is here, and generally, considered to be aself-consistent sequence of acts or operations leading to a desiredresult. These include physical manipulations of physical quantities.Usually, though not necessarily, these quantities take the form ofelectrical or magnetic signals capable of being stored, transferred,combined, compared, and otherwise manipulated. It has proven convenientat times, principally for reasons of common usage, to refer to thesesignals as bits, values, elements, symbols, characters, terms, levels,numbers or the like. It should be understood, however, that all of theseand similar terms are to be associated with the appropriate physicalquantities and are merely convenient labels applied to these quantities.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “processing,” “computing,”“calculating,” “determining,” or the like, refer to the action and/orprocesses of a computer or computing system, or similar electroniccomputing device, that manipulate and/or transform data represented asphysical, such as electronic, quantities within the computing system'sregisters and/or memories into other data similarly represented asphysical quantities within the computing system's memories, registers orother such information storage, transmission or display devices.

Embodiments of the present invention may include apparatuses forperforming the operations herein. An apparatus may be speciallyconstructed for the desired purposes, or it may comprise a generalpurpose computing device selectively activated or reconfigured by aprogram stored in the device. Such a program may be stored on a storagemedium, such as, but not limited to, any type of disk including floppydisks, optical disks, compact disc read only memories (CD-ROMs),magnetic-optical disks, read-only memories (ROMs), random accessmemories (RAMs), electrically programmable read-only memories (EPROMs),electrically erasable and programmable read only memories (EEPROMs),magnetic or optical cards, or any other type of media suitable forstoring electronic instructions, and capable of being coupled to asystem bus for a computing device.

The terms “coupled” and “connected,” along with their derivatives, maybe used herein to describe structural relationships between components.It should be understood that these terms are not intended as synonymsfor each other. Rather, in particular embodiments, “connected” may beused to indicate that two or more elements are in direct physical orelectrical contact with each other. “Coupled” my be used to indicatedthat two or more elements are in either direct or indirect (with otherintervening elements between them) physical or electrical contact witheach other, and/or that the two or more elements co-operate or interactwith each other (e.g., as in a cause an effect relationship).

Embodiments of methods and systems for controlling a process or chambercomponent temperature described herein provide a temperature controleffort including both a cooling control loop and a heating control loopin which a coolant liquid flow control and heater control arecoordinated to reduce the amount of energy required to maintain asetpoint temperature in absence of an external disturbance while stillachieving a fast control response to neutralize an external disturbance.Generally, a plasma process chamber (module) controller provides a levelof temperature control above the conventional independent heat sink/heatsource controllers. The chamber level controller executes a temperaturecontrol algorithm and communicates control parameters, such as feedbackand/or feedforward gain values to one or more of the heat sink/heatsource controllers to effect control of the coolant liquid flow controland heater duty cycle.

By moving control computations for the feedback and/or feedforwardtransfer function off an autonomous temperature control plane (e.g., adiscrete PID controller of a heat sink or heat source) and onto anintegrated control software plane of the plasma processing system whichmay compute both the feedback and feedforward control efforts, thediscrete temperature controllers of the separate heating and coolingloops may then be utilized in a coordinated manner more efficiently. Oneor more of the discrete temperature controllers may operate in a manualmode merely as a driver of the control actuators (e.g., valves,resistive elements, etc.) operating under the direction of theintegrated plasma chamber control software plane executing instructionsimplementing the temperature control system 100 depicted in FIG. 1. Inalternative embodiments however, at least one discrete temperaturecontroller is configured to operate in an automatic closed loop mode andprovide either or both of the feedback and feedforward control describedherein with the associated control computations off-loaded from theintegrated control software plane. For embodiments where one discretetemperature controller (e.g., providing a heat source) is in automaticmode, the integrated temperature control software plane may providedirections to a second discrete temperature controller (e.g., providinga heat sink) that is operating in manual mode. In either implementation,with the higher level of temperature control provided by the integratedtemperature control software plane, the cooling power, for example, maybe greatly reduced when an external temperature disturbance is absent(e.g., during idle time). Also, transition response times may bereduced, for example upon a change in setpoint temperature during activerecipe execution or idle time. This effect is achieved in certainembodiments by completely stopping a coolant liquid flow to thetemperature-controlled component to greatly reduce the cooling power andto allow relatively smaller amounts of heating power neutralize thecomponent temperature error when a feedback signal indicates thecomponent temperature is less than a setpoint temperature. With theintegrated temperature control software plane providing the ability toconditionally stop the coolant liquid flow to a chamber component,higher component setpoint temperatures may also be achieved for a givenheating power.

FIG. 1 is a block diagram illustrating a temperature control system 100including both feedforward and feedback control elements coordinatingheating and cooling control efforts 111, 112 responsive to both heatingand cooling disturbances, in accordance with an embodiment of thepresent invention. As shown, the system 100 includes a heat sourcecontrol loop 101 and a heat sink control loop 102 affecting thetemperature of a component 105. The heat source control loop 101includes a heater 390 which may be controlled by the based on a feedbackcontrol signal 108A. For exemplary embodiments which compute a controleffort based in part on a plasma power input into the plasma processingchamber, the control system 100 further provides a feedforward controlsignal 107 via the integrated control software plane becausecommercially available temperature controllers lack a feedforward inputfor disturbance compensation (e.g., instead providing only for afeedback control with inputs including a measured controlled temperature150 and setpoint temperature 106). The control signal 109 sent to theheater driver 390B therefore may be a function (e.g., summation) of boththe feedback control signal 108A and feedforward control signal 107 withan error gain and a power gain applied to the signals 108 and 107,respectively.

Similarly, the heat sink control loop 102 includes a coolant liquid flow115 which may be controlled based on a feedback control signal 108B. Forexemplary embodiments which compute a control effort based in part on aplasma power input into the plasma processing chamber, the controlsystem 100 further provides a feedforward control signal 117 via theintegrated control software plane. The control signal 119 sent to acoolant liquid control valve(s) 120 therefore may be a function (e.g.,summation) of both the feedback control signal 108B and feedforwardcontrol signal 117 with an error gain and a power gain applied to thesignals 108B and 117, respectively.

The temperature control system 100 includes at least one feedforwardtransfer function F_(A)(s), and/or F_(B)(s) which takes, as an input, aplasma power introduced into the plasma process chamber duringprocessing of a workpiece. In one such embodiment, the plasma power is aweighted sum of multiple power inputs to the processing chamber. Forexample, in one embodiment a weighted sum of Plasma Power equalsc1*P1+c2*P2+c3*P3, where P1, P2 and P3 are the bias and/or sourcepowers. The weights c1, c2, and c3 may be any real number, and aretypically positive although in certain embodiments, a weight of a sourcepower is negative where component heating is actually reduced with anincrease in source power.

The plasma power input into the feedforward line may be based on anypower output by a plasma power source, such as an RF generator,magnetron, etc., that places an appreciable heat load on the temperaturecontrolled system component. The feedforward transfer function F_(A)(s),and/or F_(B)(s) is to provide a control effort opposite in sign to thedisturbance transfer function D(s) and compensate an increase in thecontrolled temperature 150 resulting from the disturbance caused by theplasma source power heat load. The disturbance transfer function D(s)relates a heat load of the plasma power to a rise in the controlledtemperature 150 of the plasma processing chamber component having aparticular thermal time constant, π. For example, a step functionincrease in a plasma power from 0 W to 1000 W at time t may be mapped bythe disturbance transfer function D(s) to a component temperature riseover time. The feedforward control signals 107, 117 are coupled with afeedback transfer function G_(1A)(s) and/or G_(1B)(s) providing thefeedback control signal 108 for correction of an error signal εεcorresponding to a difference between the controlled temperature 150 andthe setpoint temperature 106.

The feedforward control signals 107, 117 along with the setpointtemperature 106, is input to an actuator transfer function G_(1A)(s),G_(1B)(s) and a thermal mass transfer function H(s) to compensate theeffect of the disturbance transfer function D(s) on the outputcontrolled temperature 150. The thermal mass transfer function H(s)includes a function of the heat capacities of the heat sink/source andthe temperature-controlled component, etc. The actuator transferfunction G_(2B)(s) includes a function of an actuator controlling a heattransfer between the temperature-controlled component 105 and a heatsink (e.g., chiller) and a function of the coolant flow. The illustratedembodiment further includes a function (G_(2A)(s)) of an actuatorcontrolling a heat transfer between the temperature-controlled component105 and a heat source (e.g., heater element 390 and heater driver 390B).The feedforward transfer function F_(A)(s) (or F_(B)(s)) may beimplemented with the same actuator as a conventional feedback controlsystem which may already be fitted to an independent closed loop controlsystem, such as a coolant liquid loop. An actuator may be implemented inany manner commonly employed in the art. For the exemplary coolantliquid loop embodiment, an actuator includes one or more valve(s) 120controlling the coolant liquid flow 115 coupled between thetemperature-controlled component 105 and a heat sink (e.g., chiller377). In a further embodiment, another actuator includes one or moreresistive heating element drive power switches (390B) coupled to thetemperature-controlled component 105.

FIG. 2A illustrates a schematic of a plasma etch system including atemperature controller, in accordance with an embodiment of the presentinvention. The plasma etch system 300 may be any type of highperformance etch chamber known in the art, such as, but not limited to,Enabler™, MxP®, MxP+™, Super-ETM, DPS II AdvantEdge™ G3, or E-MAX®chambers manufactured by Applied Materials of CA, USA. Othercommercially available etch chambers may be similarly controlled. Whilethe exemplary embodiments are described in the context of the plasmaetch system 300, it should be further noted that the temperature controlsystem architecture described herein is also adaptable to other plasmaprocessing systems (e.g., plasma deposition systems, etc.) which presenta heat load on a temperature-controlled component.

The plasma etch system 300 includes a grounded chamber 305. A substrate310 is loaded through an opening 315 and clamped to a chuck 320. Thesubstrate 310 may be any workpiece conventionally employed in the plasmaprocessing art and the present invention is not limited in this respect.The plasma etch system 300 includes a temperature controlled process gasshowerhead 335. In the exemplary embodiment depicted, the process gasshowerhead 335 includes a plurality of zones 364 (center) and 365(edge), each zone independently controllable to a setpoint temperature106 (FIG. 1). Other embodiments have either one zone or more than twozones. For embodiments with more than one zone, there are n heater zonesand m coolant zones where n need not be equal to m. For example, in theembodiment depicted, a single cooling loop (m=1) passes through twoheater zones (n=2). Process gases, are supplied from gas source 345through a mass flow controller 349, through the showerhead 335 and intothe interior of the chamber 305. Chamber 305 is evacuated via an exhaustvalve 351 connected to a high capacity vacuum pump stack 355.

When plasma power is applied to the chamber 305, a plasma is formed in aprocessing region over substrate 310. A plasma bias power 325 is coupledto the chuck 320 (e.g., cathode) to energize the plasma. The plasma biaspower 325 typically has a low frequency between about 2 MHz to 60 MHz,and in a particular embodiment, is in the 13.56 MHz band. In theexemplary embodiment, the plasma etch system 300 includes a secondplasma bias power 326 operating at about the 2 MHz band which isconnected to the same RF match 327 as plasma bias power 325. A plasmasource power 330 is coupled through a match 331 to a plasma generatingelement to provide high frequency source power to inductively orcapacitively energize the plasma. The plasma source power 330 typicallyhas a higher frequency than the plasma bias power 325, such as between100 and 180 MHz, and in a particular embodiment, is in the 162 MHz band.Notably, the system component to be temperature controlled by thecontrol system 100 is neither limited to the showerhead 335 or chuck 320nor must the temperature-controlled component directly couple a plasmapower into the process chamber. For example, chamber liner may betemperature controlled in the manner described herein and a temperaturecontrolled showerhead may or may not function as an RF electrode.

In the exemplary embodiment, the temperature controller 375, as theintegrated temperature control software plane of the system controller370, is to execute at least a portion of the temperature controlalgorithms described herein. As such, the temperature controller 375 maybe either software or hardware or a combination of both software andhardware. The temperature controller 375 is to output control signalsaffecting the rate of heat transfer between the showerhead 335 and aheat source and/or heat sink external to the plasma chamber 305. In theexemplary embodiment, the temperature controller 375 is coupled, eitherdirectly or indirectly, to the chiller 377 and the heater element 390. Adifference between the temperature of the chiller 377 and the setpointtemperature 106 may be input into the feedforward control line alongwith the plasma power.

The chiller 377 is to provide a cooling power to the showerhead 335 viaa coolant loop 376 thermally coupling the showerhead 335 with thechiller 377. In the exemplary embodiment, one coolant loop 376 isemployed which passes a cold liquid (e.g., 50% ethylene glycol at asetpoint temperature of −15° C.) through a coolant channel embedded inboth the inner zone 364 and outer zone 365 (e.g., entering proximate toa first zone and exiting proximate to the other zone) of the showerhead335. The ability to have such low coolant setpoint temperatures is abenefit of the pulsed cooling control system described herein overconventional systems which must maintain a minimum coolant flow rate(e.g., 0.8 GPM) to avoid fluid stagnation even under low/no plasma powerconditions. To ensure no more heat is extracted than the heat source canprovide under low/no plasma power conditions, the minimum coolantsetpoint temperature is limited by this non-zero minimum flow rate. Withthe pulsed cooling control system, however, because the duty cycle ofcoolant may be set to very low percentage, even 0% under idle control,the coolant sink is enabled to operate at a lower setpoint for increasedsink capacity.

The temperature controller 375 is coupled to a coolant liquid pulsewidth modulation (PWM) driver 380. The coolant liquid PWM driver 380 maybe of any type commonly available and configurable to operate thevalve(s) 120 for embodiments where those valves are digital (i.e.,having binary states; either fully open or fully closed) at a duty cycledependent on control signals sent by the temperature controller 375. Forexample, the PWM signal can be produced by a digital output port of acomputer (e.g., controller 370) and that signal can be used to drive arelay that controls the valves to on/off positions. Alternatively, asfurther depicted by FIG. 2B, a heater controller 391 which supports PWMfunctionality and provides for external drive of a commanded duty cyclethereby also providing at least some of the functionality of the coolantliquid PWM driver 380 and negating the need for two separate PWMinterfaces. In still other embodiments, analog valves providing aninfinitely variable flow rate from 0 to a maximum flow rate are utilizedwith the valve open positions controlled by the temperature controller375.

For the exemplary embodiment depicted in FIG. 2A, the heater element 390depicted in FIG. 1 includes first and second electrical resistiveheating elements 378, 379. The heating elements 378, 379 may beindependently driven based on one or more temperature sensors 366 and367 (e.g., an optical probe in each of the inner and outer zones 364,365). The heater driver 390B may be a solid state relay or asemiconductor controlled rectifier (SCR), for example. The heatercontroller 391 provides PWM functionality analogous to, or in place of,coolant liquid PWM driver 380 to interface the temperature controller375 with either or both of the heater element(s) 378, 379 and thecoolant loop 376. For example, units commercially available from WatlowElectric Manufacturing Company, USA or Azbil/Yamatake, Japan, may beemployed as the heater controller 391 and/or coolant liquid PWM driver380.

Referring to FIG. 2B, in a manual mode, duty cycle control commands aresent (e.g., serially) by the temperature controller 375 to the heatercontroller 391. The heater controller 391, via the PWM driver 393,outputs a square wave at the prescribed duty cycle to the heater driver390B. Reference to “manual mode” is with respect to the heatercontroller 391 being in an open loop with the temperature controller 375sending control commands to the heater controller 391 for automaticcontrol of heater power. For analog embodiments, an analog signal may besent to the heater driver 390B which would turn on/off the heaterelement(s) at an appropriate AC phase, for example at zero crossing. Forthe exemplary embodiment with two heater zones, two channels of theheater controller 391 are output to the heater driver 390B for elements378, 379. In a further embodiment, where the heater controller 391 alsoprovides the functionality of the liquid coolant PWM driver 380, one ormore channels (e.g., a third channel) from the heater controller 391 isoutput to operate the coolant valve(s) 120 (e.g., switch the valve(s)120 on/off via an electronic to pneumatic transducer). As such, whencooling is required, the valve(s) 120 may be opened (e.g., duty cycleincreased) and when heating is required, the valve(s) 120 may be closed(e.g., duty cycle decreased) and resistive heating elements 378 and/or379 driven. As described elsewhere herein, this “manual mode” may beutilized to control a component temperature during an active recipe stepat the process recipe control level via the temperature controller 375.

In an automatic control mode, heater controller 391 provides thefunctionality of an independent/closed loop PID controller, via PID 392,which operates the heaters based on the temperature information receiveddirectly (e.g., via temperature sensors 366, 367), the setpointtemperature (e.g., from recipe file), and further based on gain valuesreceived from the temperature controller 375. In an embodiment, theautomatic control operates the heater 390 during an idle mode, asdescribed elsewhere herein. Whether the heater controller 391 is inautomatic or manual control mode however, for embodiments where theheater controller 391 further interfaces the temperature controller 375with the coolant loop valve(s) 120, the coolant duty cycle is preferablydetermined by the temperature controller 375 and not the heatercontroller 391.

Notably, the temperature controller 375 need not be contained within, orprovided by, the integrated process chamber control software plane ofthe system controller 370. Specifically, the functionality oftemperature controller 375 may be instead provided as discrete system.For example, PID controllers, such as, but not limited to thosecommercially available from Watlow Electric Manufacturing Company orAzbil of Yamatake Corp., may be designed to include additionalfeedforward inputs, such as the plasma power. The discrete system mayfurther be manufactured to include a processor having the ability todetermine a feedforward control effort based on those feedforwardinputs. As such, all the embodiments described herein for temperaturecontrol may be provided either by the temperature controller 375 as afacet of an integrated process chamber control software plane or as acomponent of the PWM driver 380 and/or heater controller 391.

In an embodiment, to reduce the cooling power during system idle time(i.e., when no plasma processing is occurring in the chamber 305) thetemperature controller 375 maintains control over the cooling loop 101during both an idle state (e.g., no substrate processing being performedby chamber) and an active state (e.g., substrate processing beingperformed). FIG. 3A is a state diagram 300 illustrating control loopconfigurations for an idle state 311 and an active state 321 of a plasmaprocessing chamber, in accordance with an embodiment of the presentinvention. As shown, while in the idle state 311, the system operates inan event driven mode during which interlocks 340 may be triggered uponthe occurrence of events defined in an interlock table. In anembodiment, the coolant liquid flow is determined based on correspondingtemperature threshold values of the component 105 (e.g., showerhead 335)defined in the interlock table illustrated in FIG. 4A.

FIG. 4A illustrates an event driven control algorithm for controlling acomponent temperature during an idle state. As shown, in response to afeedback signal indicating the chamber component temperature is below asetpoint temperature 401 (T_(SP)) the coolant liquid flow into thetemperature-controlled component (e.g., showerhead 335) is set to afirst duty cycle (IDLE DCO). In a particular embodiment, this first dutycycle IDLE DCO reduces the coolant liquid flow rate to zero tocompletely stop the flow to the component if the temperature is belowthe threshold 402 (T_(SP)+delta T1). Upon crossing the thresholds 402,403 and 404, the duty cycle is changed to IDLE DC1, DC2, DC3, etc.,depending on the temperature rising or falling. As such, if a setpointtemperature is raised during the idle state 311 (e.g., in preparationfor another process), the coolant flow is stopped and heater power(e.g., operating in automatic mode) has a faster effect and highersetpoint temperatures may be achieved.

In the particular embodiment depicted in FIG. 3A, when the system movesinto the idle state 311 from an active state 321, the heater 390 isplaced into an automatic, closed loop mode 314. For such an embodiment,the heater controller (e.g., PID 392 of FIG. 2B) seeks to achieve thesetpoint temperature 106 by driving the heating elements as needed whilethe temperature controller 375 sends control commands for the valve(s)120 to the PWM driver 393 to close the heat sink control loop 102 with afeedback signal. As further depicted in FIG. 3A, when the system movesinto the active state 321 from the idle state 311, the heater 390 isplaced into the manual mode. For such an embodiment, duty cycles forboth heater power and valve(s) 120 are determined by the temperaturecontroller 375 to close the both the heat sink control loop 102 and heatsource control loop 101 with a feedback and/or a feedforward signal.Notably, however, in either active or idle states, the controller 375preferably determines the duty cycle for the liquid coolant.

Returning to FIG. 3A, when in the system active state 321, the systemoperates in a recipe driven mode during which coolant and heaterparameters from a recipe control algorithm may be executed on a time orprocessor cycle basis. FIG. 3B is a block diagram illustratingparticular segments in a plasma processing recipe executed during activestates 321A and 321B before and after an idle state 311, in accordancewith an embodiment of the present invention. In the active state 321A, aplasma process recipe executing has a recipe step N (301) and asubsequent recipe step N+1 (302) which, for example, may be the last twoplasma etch recipes steps of a continuous plasma process recipe duringwhich plasma power is input into a plasma chamber. Unlike the idle state311 which employs a feedback control algorithm such as that depicted inFIG. 4A, during execution of recipe step N (301) the coolant and heatercontrol parameters are determined at least in part with a controlalgorithm, such as that depicted in FIG. 4B, which utilizes afeedforward signal. When the recipe step N+1 (302) is subsequentlyexecuted by the plasma processing system, the coolant and heater controlparameters are similarly determined by a feedforward control algorithm(e.g., FIG. 4B). In the exemplary embodiment illustrated, the recipestep N (301) includes a first portion 301A and a second portion 301Bwhich allow for a plurality of independent temperature controlparameters (e.g., control gain groups for closed loop operation or dutycycle values for open loop operation) within the single recipe step N(301). The second portion 301B may be considered a “look-ahead” portionwhich allows for the an open loop set of temperature control parametersto be implemented before the duration of recipe step N (301) ends inpreparation for the subsequent recipe step N+1 (302). Thus, uponentering the recipe step N (301), a closed loop gain group for the firstportion 301A and open loop heater and/or coolant flow duty cyclevalue(s) for the second portion 301B may be determined from a database,lookup table, or the like. Such lookup tables may provide duty cyclevalues which are associated with particular plasma input powers.

As further depicted in FIG. 3B, the active state 321 may include apost-recipe step 303 in which closed or open loop control is continuedafter a plasma power is no longer input into the processing chamber(i.e. plasma processing completed). The post-recipe step 303 continueseither closed loop or open loop temperature control for an extendedperiod of time and may allow for a change in the setpoint temperaturebefore a workpiece is unloaded from a processing chamber. During thepost-recipe step 303, the minimum coolant fluid flow threshold ismaintained during a substrate transfer until the next recipe starts.Similarly, the active state 321 may include a pre-recipe step 307 priorto performance of a first recipe step 308 in which plasma power isintroduced for the first time in a process recipe. The pre-recipe step307 allows closed or open loop control for an extended period of timewhich may allow for a change in the setpoint temperature before aworkpiece is processed in a processing chamber.

During active state 321, a minimum coolant fluid flow threshold may beestablished to ensure the coolant flow is sufficiently high for a rapidtemperature control response as may be required in subsequent recipesteps. With the coolant fluid flow maintained above the minimum coolantfluid flow threshold, a response delay which otherwise might result ifcoolant fluid stagnates may be avoided. For example, for a 90° C.setpoint, minimum duty cycle may be 15-20%. In one embodiment, theminimum coolant fluid flow threshold is a function of setpointtemperature 106 with a higher threshold for higher temperature setpoint.

Demarking the transition between active state 321 and idle state 311 isa delay time 309 before the idle state temperature control mode (e.g.,FIG. 4A) is entered. If this delay time 309 is 0 seconds, then thesystem goes into idle control mode immediately after finishing a recipe.Otherwise, the actuator commands (e.g., the coolant flow and or heaterpower duty cycles) remain the same as was applied during the post recipestep 303. In certain embodiments, while in the idle state 311, coolantflow is completely shut off (i.e., duty cycle of 0%) further reducingheater power requirements and allowing the heater controller 391 tooffset only ambient heat sinking during closed loop componenttemperature control.

As further shown in FIG. 3C, upon the powering down the heater 390,temperature control may be taken offline automatically via method 350.For example when the chamber is taken offline for servicing, thetemperature controller 375 automatically sets the coolant fluid flowrate to a predetermined “shutoff” value at operation 355 to ensure acontrolled ramp down of the component temperature. A controlled ramprate may be predetermined based on the component, for example for ashowerhead having laminated structure may require a given rate to avoidwarping and stress-induced delamination. At operation 355, the coolantfluid flows at the shutoff value until the temperature of component(e.g., inner or outer showerhead zone) reaches a threshold temperatureor a threshold difference between the coolant fluid temperature and thecomponent temperature, upon which the coolant fluid flow rate isstopped. For example, where the coolant fluid temperature is 20° C., athreshold difference between the coolant fluid temperature and ashowerhead temperature is set to 10° C., and a coolant fluid shutoffduty cycle is 15%, coolant will flow through the showerhead at the 15%duty cycle until the temperature of showerhead (inner or outer) is lessthan 30° C. (20+10). Once the showerhead is less than 30° C., coolantfluid flow is stopped.

Referring back to FIG. 3A, in embodiments, a group of gain valuesincluding at least a feedforward control signal gain and a feedbackcontrol signal gain is determined by the temperature controller 375based on at least the plasma power input into the chamber 305 for acurrent recipe step. In one such embodiment, a first group of gainvalues associated with a key value pairing of the plasma input power andthe setpoint temperature is determined for the first portion 301A of theexecuting recipe step 301. FIG. 4C illustrates a gain group lookuptable, in accordance with an embodiment of the present invention. Asshown, setpoint temperature 486 is a first key value and plasma powerinput 485 is a second key value. Gain groups 1, 2, 3, etc. containinggain values for the various control signals in system 100 may bedetermined from the temperatures 486, plasma power inputs 485 or apairing of the two corresponding to the conditions of the executingrecipe step. The gain group may then be applied as further describedelsewhere herein with reference to FIG. 4B.

To provide a faster transition to the subsequent recipe step N+1 (302),duty cycle values for the second portion 301B of the executing recipestep may be determined for either or both of the coolant controlvalve(s) 120 and the heater 390 upon initiating the recipe step N (301).As such, one or both of the heat source control loop 101 and heat sinkcontrol loop 102 may be placed into open loop control modes during thesecond portion 301B of the recipe step N (301). While the duration ofthe second portion 301B may be a fixed time, in a further embodiment,the duration of the second portion 301B is dependent on a change in thesetpoint temperature and/or change in plasma power that is to occurbetween the currently executed recipe step N (301) and recipe step N+1(302) to be subsequently executed.

In an embodiment where temperatures of the component 105 are changedbetween steps of an executing recipe (e.g., to help control polymerdeposition), transient specific control parameters may be determined andcommunicated by the temperature controller 375. FIG. 4D illustrates atransient control period 494 for addressing changes in setpointtemperatures between two steps in a plasma process recipe, in accordancewith an embodiment of the present invention. The recipe step N (301) andrecipe step N+1 (302) are illustrated with the recipe step 492 along thex-axis and setpoint temperature 491 along the y-axis. In the depictedexample, a plasma input power of 1000 W is applied during the recipestep N (301) while the setpoint temperature is 30° C. For the recipestep N+1 (302), 5000 W of plasma power is applied with a setpointtemperature of 50° C. In one embodiment where the duration of thetransient control period 494 is dependent on a change in the setpointtemperature and/or change in plasma power, a transient response gaingroup (e.g., defining high gain values) is applied for an amount of timerequired to achieve a percentage of the change in setpoint temperature.For the example, in FIG. 4D, the transient control period 494 occurs for90% of the 20° C. rise in temperature between step N (301) and step N+1(302), or until the temperature reaches the threshold 493 (48° C.). Assuch, this transient group of gain values is applied for a durationwhich is longer when there is a greater change in setpoint temperature.A similar algorithm may be applied based on the magnitude of change inplasma power, for example increasing the duration of the transientcontrol period 494 with greater changes in plasma power between steps.Alternatively, the transient control parameters may simply be appliedfor fixed time.

In an embodiment, transient response gain groups are associated with atleast one of a change in plasma input power or a change in the setpointtemperature and may further be associated with a key value pairing achange in the plasma input power with a change in the setpointtemperature. FIG. 4E, for example, illustrates a lookup table for atransient gain group employed by the control transient control period494 in FIG. 4D. As shown in FIG. 4E, a gain group is associated withchanges of plasma input power 496 and changes of setpoint temperature495.

In further embodiments, heater gain groups may also be determined for,and utilized, in the idle state 311. For example, a gain group may bedetermined from the lookup table illustrated in FIG. 4C during the idlestate 311 as described for active state 321 when the heater controller391 is in auto mode (e.g., during for the first recipe step portion301A). Plasma power, which will be zero during the idle state 311, ispaired with setpoint temperature to determine a gain group for a givenidle state 311.

FIG. 4B is a flow diagram illustrating operations in a method forcontrolling a component temperature with the control system described inFIG. 1 during an active state, in accordance with an embodiment of thepresent invention. The method 450 begins at operation 451 withdetermination of the gain group as well as any “look-ahead” details(duration of 301B, duty cycle values for coolant liquid flow valve(s)120, duty cycles for either or both of the inner and outer resistiveheater elements 378, 379). With the passage of a sample time T_(calc) atoperation 455, the current controlled temperature 150 (FIG. 1) isacquired, the setpoint temperature 106 is acquired, and the plasma inputpower is acquired at operation 460. A setpoint temperature for the heatsink may also be acquired. In the exemplary embodiment depicted in FIG.2, the temperature controller 375 receives a controlled temperatureinput signal from showerhead sensors for inner and outer zones 364, 365.The temperature controller 375 acquires a setpoint temperature from aprocess recipe file, for example stored in the memory 373, and thetemperature controller 375 acquires a setpoint or measured plasma poweras described elsewhere herein.

In a preferred embodiment, a measured forward bias power 328 energizinga plasma in the process chamber 305 at the current time (e.g., afterpassage of T_(calc)) is input into the feedforward control line as aplasma heat load (e.g., Watts). Plasma power setpoint values (e.g., froma process recipe file stored in a memory 373) may also be utilized as aninput to the feedforward control line. Such power setpoint values, beingpredefined, may enable the feedforward transfer function F_(A)(s),and/or F_(B)(s) to be evaluated for the power setpoint prior toapplication of plasma power or prior to a change in the application ofplasma power into the system and generate an anticipatory controleffort. However, assuming the temperature control system 100 can reactsufficiently quickly, the plasma power input is preferably coupled to ameasured power output signal for greater accuracy of the plasma powerapplied at current time. Even for such embodiments, control effortdeterminations for future time (e.g., recipe step N+1 (302)) wouldremain recipe-based.

In an embodiment, the plasma power input comprises a first bias powerinput to the chamber 305. For example, the plasma power input may be setequal to the plasma bias power 325 (FIG. 2A). For embodiments where theplasma processing system applies a plurality of bias power inputs to achamber, the sum of the plurality of bias powers is input to thetemperature control system 100. For example, in the exemplary embodimentdepicted in FIG. 2A, a weighted sum of the plasma bias powers 325 and326 are input. With the first and/or second, etc. plasma bias powers asthe plasma power input, the feedforward transfer function F_(A)(s),and/or F_(B)(s) relates the bias power input (e.g., measured as forwardbias power 328 output from RF match 327) to the feedforward controlsignal u defining a cooling effort to compensate the disturbancetransfer function D(s).

Although in the exemplary embodiment the plasma power input p(s) is thesum of the bias powers, it should be noted that the determination of thefeedforward control signal u may exclude one or more of the plasma powersource. For example, referring to FIG. 2A, a high frequency plasmasource power 330 may be excluded because the heat load placed on theshowerhead 335 (or chuck 320) is relatively small. In alternativeembodiments however, where the temperature to be controlled has anappreciable dependence on all plasma power input into a processingchamber, the feedforward control signal u output from the feedforwardtransfer function F_(A)(s), and/or F_(B)(s) may be further based on theplasma source power 330. For example, a power weighting function may beapplied, such as c1*P1+c2*P2+c3*P3, as described elsewhere herein.

Returning to FIG. 4B, at operation 465, the feedforward control signalu, the temperature error signal ε (T-T_(sp)), the feedback controlsignal v, and the look-ahead duty cycles are computed at every T_(calc)(e.g., by the CPU 372 executing the method 450 as an instance oftemperature controller 375 stored in the memory 373). For the exemplaryembodiment depicted in FIG. 2A having both an inner and an outershowerhead zone 364, 365, each of the feedforward control signal u, thetemperature error signal ε, the feedback control signal v, and thelook-ahead duty cycle is computed for each zone.

In the Laplace domain

u(s)=F(s)p(s),

where u is the feedforward signal, F is the Feedforward transferfunction and p is the plasma power. For the embodiment depicted in FIG.2A, the feedforward control signal u may be implemented in discrete timedomain as:

u(t) = β_(o)P(t) + β₁P(t − T_(PWM)) + β₂P(t − 2T_(PWM)) + …  α₁u(t − T_(PWM)) + α₂u(t − 2T_(PWM)) + α₃u(t − 3T_(PWM)) + …

where P(t) is the plasma power input at the current T_(calc), and whereT_(PWM) is a time increment of the PWM driver 380, 393. In a particularembodiment, feedforward control signal u is computed as simply β_(o)P(t)to be based on the plasma power input at the current time (e.g.,T_(calc)).

In a further embodiment, because the plasma power to be requested infuture time periods is determinable (e.g., from the process recipefile), the feedforward expression further includes the termsθ₁P(t+T_(PWM))+θ₂P(t+2T_(PWM)) to compensate for lag in the effect of thcoolant flow on the controlled temperature. In another embodiment, theheat transfer required to achieve the controlled temperature 150 isdependent on the heat sink (e.g., chiller 377) setpoint temperatureand/or heat source(e.g., heat exchanger 378) setpoint temperature suchthat the additional coolant temperature dependent termδ_(c)(T_(SP)−T_(heatsink))+δ_(h)(T_(SP)−T_(heatsource)) added to thefeedforward control signal u, where T_(SP) is the controlled temperature150. Each of δ_(c) and δ_(h) may be defined as a polynomial function ofthe temperature difference between the setpoint and the heat sink/heatsource. For example, in one embodimentδ_(c)×α₀+α₁(T_(SP)−T_(heat sink))+α₂(T_(SP)−T_(heat sink))²+α₃(T_(SP)−T_(heat sink))³with δ_(h) taking a similar form. The entire feedforward equation canalso have factors for temperature dependence, Ω_(hot) and Ω_(cold), suchthat the net feedforward control signal u becomes:

u(t) = Ω_(hot)(T_(SP) − T_(heat  soure))Ω_(cold)(T_(SP) − T_(heat  sink)){β_(o)P(t) + β₁P(t − T_(PWM)) + β₂P(t − 2T_(PWM)) + …  α₁u(t − T_(PWM)) + α₂u(t − 2T_(PWM)) + α₃u(t − 3T_(PWM)) + …  θ₁P(t + T_(PWM)) + θ₂P(t + 2T_(PWM)) + δ_(c)(T_(SP) − T_(heat  sink)) + δ_(h)(T_(SP) − T_(heat  source))}.

Similarly, the feedback control signal v is v(t)=G(s)ε(s) in the Laplacedomain and may be implemented in discrete time domain as:

v(t) = λ₀e(t) + λ₁e(t − T_(PWM)) + λ₂P(t − 2T_(PWM)) + …  η₁v(t − T_(PWM)) + η₂v(t − 2T_(PWM)) + η₃v(t − 3T_(PWM)) + …

Where ε(t) is the temperature error signal (difference betweencontrolled temperature 150 and setpoint temperature 106) at T_(calc). Ina particular embodiment, feedback control signal v is computed as simplyλ_(o)e(t). While the operation 465 is performed every T_(calc), thecontrol computations are to use input temperatures and plasma powervalues input at some lower frequency corresponding to times t,t-T_(PWM), etc. Values for the parameters of u, v, plasma power (P),controlled temperature 150, and setpoint temperature 106 may be storedin a data array and those stored values corresponding to the discretetimes of t, t-T_(PWM) may then be utilized in subsequent controlcalculations.

For recipe steps employing the second portion 301B to provide look-aheadopen loop control, the look-ahead duty cycle is determined from for alookup table, database, etc., as described elsewhere herein. Atoperation 470, a control actuator output signal p (e.g., duty cycle) isdetermined for each of the heater 390 and coolant flow coolant liquidflow valve(s) 120 and then output to the actuator at operation 475.

In one embodiment, a constant gain K_(ν) (e.g., one of the gains makingup a gain group in FIG. 4C) is applied to the feedforward control signalu and a constant gain K_(u) is applied to the feedback control signal vsuch that the control actuator output signal ρ is calculated asρ(t)=K_(ν)ν−K_(u)u. The gain groups containing K_(ν), K_(u) provide asystem operator a simple interface to access the combined feedforwardand feedback control line in two simple factors for each of the heatsource control loop 101 and heat sink control loop 102. Depending on thevalue of the control actuator output signal Σ, heat transfer between oneor more of a heat sink and heat source is modulated. In exemplaryembodiment of FIG. 2A therefore, where the control actuator outputsignal Σ is of a first sign (e.g., Σ<0), the controlled temperature 150may be reduced via a command provided by the temperature controller 375in a form executable by the PWM driver 380 or 393 to increase the dutycycle of the valve(s) 120 and increase the heat transfer between thechiller 377 and the showerhead 335 while the heater 390 reduces the dutycycle of the resistive heating elements 378 and/or 379. This situationwould be typical for a recipe step in which plasma power is on or asetpoint temperature has been reduced.

Where the control actuator output signal Σ is of a second sign (e.g.,Σ>0), the controlled temperature 150 may be increased via a commandprovided by the temperature controller 375 in a form executable by thePWM driver 380 or PWM driver 393 to reduce the duty cycle of thevalve(s) 120 and reduce the heat transfer between the chiller 377 andthe showerhead 335 while the duty cycle of the resistive heatingelements 378 and/or 379 is increased. For example, where a recipe stepin which plasma power is reduced from a previous level (e.g., turnedoff) or where a setpoint temperature is decreased while the total plasmapower is constant, Σ changes from a more negative number to a lessnegative number, then the coolant flow from chiller 377 is reduced bydecreasing the duty cycle of valve(s) 120. In particular embodiments,while a heating power input to heat the chamber component is increased,a coolant liquid flow between the process chamber and a heat sinkexternal to the process chamber is reduced to a flow rate of zero inresponse to the feedback signal v. Thus, in certain embodiments, acomplete stoppage of the coolant fluid to the temperature-controlledcomponent (e.g., showerhead 335) may occur in response to the componenttemperature being below the setpoint temperature during either the idlestate 311 or active state 321. During the active state 321, thiscapability allows for faster transient response times and higherpossible operating temperatures while in the idle state 311, less heaterpower is wasted. In other embodiments, complete stoppage of the coolantfluid to the temperature-controlled component (e.g., showerhead 335)occurs in response to the component temperature being below the setpointtemperature during only the idle state 311 with a minimum coolant fluidflow threshold limiting the coolant fluid to a non-zero value, asdescribed elsewhere herein.

For the exemplary embodiment depicted in FIG. 2A, the presence of theinner and outer zones 364 and 365 is complicated by the two zones havingin common the single coolant loop 376. In a particular embodiment, withthe control actuator control signal Σ calculated independently for allheater zones, the control actuator command determination may includelogic to handle conditions where a computation for the first zone (e.g.,inner zone 364) determines a coolant fluid duty cycle different fromthat computed for the second zone (e.g., outer zone 365). For example,thresholds may be established for differences in the duty cyclesdetermined for each of the coolant liquid flow and heater powers and/orconditions for the separate zones combined as a Boolean OR such that thecoolant flow duty cycle may default to a non-zero flow value even if onezone requires heating. In the exemplary embodiment depicted in FIG. 2A,if Σ_(inner) and Σ_(outer)>0, coolant duty cycle is non-zero and heaterduty cycles=0. If Σ_(inner)>0 and Σ_(outer)<0, then cool inner and heatouter (coolant will flow through both zones for exemplary embodimentwith common cooling loop shared between inner and outer zones 364, 365).If Σ_(inner)<0 and Σ_(outer)>0, then inner zone 364 is heated and outerzone 365 is cooled (coolant will flow through both zones for exemplaryembodiment with common cooling loop shared between inner and outer zones364, 365). If Σ_(inner)<0 and Σ_(outer) <0, then inner and outer zones364, 365 are heated (coolant fluid flow duty cycle=0).

In a particular embodiment, with the control actuator control signal Σcalculated independently for all heater zones, the duty cycle of coolantliquid passing through all heater zones (e.g., inner and outer zones364, 365) is a determined as a function of a maximum duty cycle betweenthe heater zones, a minimum duty cycle between the heater zones, a dutycycle of the inner zone 364, and a duty cycle of the outer zone 365. Forexample, the coolant liquid duty cycle may be determined as:CoolantGain*abs(dutycycle_(inner)*Σ_(inner)+dutycycle_(outer)*Σ_(outer)+dutycycle_(max)*max(Σ_(inner),Σ_(outer))+dutycycle_(min)*min(Σ_(inner),Σ_(outer))),where CoolantGain is a factor to amplify or attenuate Σ anddutycycle_(inner), dutycycle_(outer), dutycycle_(max), anddutycycle_(min) are correction factors for the coolant duty cycle basedon the heater power for the particular zone.

It is therefore possible under certain circumstances that both heatingpower and coolant fluid flow is non-zero (e.g., in the case where zones364 and 365 are disturbed differently or have significantly differentsetpoint temperatures 106). For example, where the inner zone 364 (firstzone) needs heating to reach a higher setpoint while the outer zone 365(second zone) is to be cooled to reach a lower setpoint temperature,then coolant flow would be based on the outer zone 365 that requirescooling with extra heating applied to inner zone 364 to overcome thecoolant flowing the first zone. A such, the inner and outer zone heaterduty cycles may be determined as:

HeaterDutyCycle_(inner)=HeaterGain_(inner)*abs(Σ_(inner)); and

HeaterDutyCycle_(outer)=HeaterGain_(outer)*abs(Σ_(outer))*correction2_(outer)*Σ_(inner)²+correction1_(outer)*Σ_(inner)+correction0_(outer), where HeaterGain isa factor to amplify or attenuate Σ for a particular heater zone.

FIG. 5 illustrates a diagrammatic representation of a machine in theexemplary form of a computer system 500 which may be utilized to performthe temperature control operations described herein. In one embodiment,the computer system 500 may be provisioned as the controller 370 in theplasma etch system 300. In alternative embodiments, the machine may beconnected (e.g., networked) to other machines in a Local Area Network(LAN), an intranet, an extranet, or the Internet. The machine mayoperate in the capacity of a server or a client machine in aclient-server network environment, or as a peer machine in apeer-to-peer (or distributed) network environment. The machine may be apersonal computer (PC), a tablet PC, a set-top box (STB), a PersonalDigital Assistant (PDA), a cellular telephone, a web appliance, aserver, a network router, switch or bridge, or any machine capable ofexecuting a set of instructions (sequential or otherwise) that specifyactions to be taken by that machine. Further, while only a singlemachine is illustrated, the term “machine” shall also be taken toinclude any collection of machines (e.g., computers) that individuallyor jointly execute a set (or multiple sets) of instructions to performany one or more of the methodologies discussed herein.

The exemplary computer system 500 includes a processor 502, a mainmemory 504 (e.g., read-only memory (ROM), flash memory, dynamic randomaccess memory (DRAM) such as synchronous DRAM (SDRAM) or Rambus DRAM(RDRAM), etc.), a static memory 506 (e.g., flash memory, static randomaccess memory (SRAM), etc.), and a secondary memory 518 (e.g., a datastorage device), which communicate with each other via a bus 530.

The processor 502 represents one or more general-purpose processingdevices such as a microprocessor, central processing unit, or the like.More particularly, the processor 502 may be a complex instruction setcomputing (CISC) microprocessor, reduced instruction set computing(RISC) microprocessor, very long instruction word (VLIW) microprocessor,processor implementing other instruction sets, or processorsimplementing a combination of instruction sets. The processor 502 mayalso be one or more special-purpose processing devices such as anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA), a digital signal processor (DSP), network processor,or the like. The processor 502 is configured to execute the processinglogic 526 for performing the temperature control operations discussedelsewhere herein.

The computer system 500 may further include a network interface device508. The computer system 500 also may include a video display unit 510(e.g., a liquid crystal display (LCD) or a cathode ray tube (CRT)), analphanumeric input device 512 (e.g., a keyboard), a cursor controldevice 514 (e.g., a mouse), and a signal generation device 516 (e.g., aspeaker).

The secondary memory 518 may include a machine-accessible storage medium(or more specifically a non-transitory computer-readable storage medium)531 on which is stored one or more sets of instructions (e.g., software522) embodying any one or more of the temperature control algorithmsdescribed herein. The software 522 may also reside, completely or atleast partially, within the main memory 504 and/or within the processor502 during execution thereof by the computer system 500, the main memory504 and the processor 502 also constituting machine-readable storagemedia. The software 522 may further be transmitted or received over anetwork 520 via the network interface device 508.

The machine-accessible storage medium 531 may further be used to store aset of instructions for execution by a processing system and that causethe system to perform any one or more of the temperature controlalgorithms described herein. Embodiments of the present invention mayfurther be provided as a computer program product, or software, whichmay include a machine-readable medium having stored thereoninstructions, which may be used to program a computer system (or otherelectronic devices) to control a plasma processing chamber temperatureaccording to the present invention as described elsewhere herein. Amachine-readable medium includes any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputer). For example, a machine-readable (e.g., computer-readable)medium includes a machine (e.g., a computer) readable storage medium(e.g., read only memory (“ROM”), random access memory (“RAM”), magneticdisk storage media, optical storage media, and flash memory devices,etc.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Many other embodiments will beapparent to those of skill in the art upon reading and understanding theabove description. Although the present invention has been describedwith reference to specific exemplary embodiments, it will be recognizedthat the invention is not limited to the embodiments described, but canbe practiced with modification and alteration within the spirit andscope of the appended claims. Accordingly, the specification anddrawings are to be regarded in an illustrative sense rather than arestrictive sense. The scope of the invention should, therefore, bedetermined with reference to the appended claims, along with the fullscope of equivalents to which such claims are entitled.

What is claimed is:
 1. A method for controlling a plasma process chambercomponent temperature, the method comprising: generating a feedbacksignal indicating the chamber component temperature is below a setpointtemperature; and reducing a coolant liquid flow between the processchamber and a heat sink external to the process chamber to a flow rateof zero in response to the feedback signal.
 2. The method of claim 1,further comprising: determining a plasma power input to the processchamber when the chamber is in an active state executing a plasmaprocess recipe; and controlling the coolant liquid flow with afeedforward control signal based on the input plasma power.
 3. Themethod of claim 2, further comprising: controlling a heating power inputto the chamber component with a feedforward control signal based on theinput plasma power.
 4. The method of claim 3, wherein controlling thecoolant liquid flow and the heating power input further comprisesapplying a first group of gain values during a first portion of anexecuting step in the plasma process recipe, the first group of gainvalues associated with a key value pairing of the plasma input power andthe setpoint temperature for the executing recipe step, wherein the gainvalue group includes at least a feedforward control signal gain and afeedback control signal gain.
 5. The method of claim 4, whereincontrolling the coolant liquid flow and the heating power input furthercomprises applying a group of transient gain values during a secondportion of the executing recipe step, the group of transient gain valuesassociated with a key value pairing of a change in the plasma inputpower and a change in the setpoint temperature between the executingstep and a subsequent plasma process recipe step.
 6. The method of claim5, wherein the group of transient gain values are applied for a durationdependent on the chamber component temperature and the change in thesetpoint temperature.
 7. The method of claim 4, wherein controlling thecoolant liquid flow and the heating power input further comprisesdetermining a coolant liquid flow duty cycle or a heating power inputfrom a look up table during a second portion of the executing recipestep.
 8. The method of claim 2, further comprising: setting the liquidcoolant flow rate based on a lookup table value in response to thecomponent temperature crossing a threshold level when the chamber is inan idle state.
 9. The method of claim 1, further comprising setting thecoolant liquid flow to a non-zero value in response to a heater powerinput to the chamber component being reduced to zero.
 10. The method ofclaim 5, wherein the plasma power comprises a first bias power input toa chuck configured to support a workpiece and wherein the feedforwardcontrol signal comprises a transfer function between the bias powerinput and the showerhead temperature.
 11. The method of claim 1, whereincontrolling the coolant liquid flow further comprises modulating a pulsewidth modulation duty cycle to fully open and fully close a valvethrough which the coolant liquid flows, and wherein the controlling ofcoolant liquid flow is constrained to a non-zero minimum flow rate whilethe chamber is in an active state.
 12. A computer readable media withinstructions stored thereon, which when executed by a processing system,cause the system to perform the method of claim
 1. 13. A plasmaprocessing apparatus, comprising: a plasma power source coupled to theprocess chamber to energize a plasma during processing of a workpiecedisposed in the process chamber; a process chamber including atemperature-controlled component coupled to a heat sink by a coolantliquid loop, the coolant liquid loop including a coolant liquid controlvalve which completely stops the coolant liquid flow to thetemperature-controlled component; and a temperature controller coupledto the coolant liquid control valve to control a heat transfer betweenthe temperature-controlled component and the heat sink by varying thecoolant liquid flow rate over a range including zero liquid flow. 14.The apparatus of claim 13, wherein the temperature controller includes afeedforward control line for control of the coolant liquid controlvalve, wherein the temperature controller is communicatively coupled tothe plasma power source, and wherein a feedforward control signal isbased on a plasma power input to energizing the plasma.
 15. Theapparatus of claim 13, wherein the temperature-controlled component isfurther coupled to a heat source and wherein the temperature controlleris to coordinate with the coolant liquid flow a control of the heattransfer between the heat source and the temperature-controlledcomponent.
 16. The apparatus of claim 15, further comprising a heatercontroller communicatively coupled to the temperature controller,wherein the heater controller is coupled to a resistive heating elementdriver and the coolant liquid control valve to control both the heatingpower and the cooling power in response to commands received from thetemperature controller.
 17. The apparatus of claim 13, wherein thetemperature-controlled component is a process gas showerhead and whereinthe coolant loop passes through a coolant channel embedded in theshowerhead.
 18. The apparatus of claim 17, wherein m independentlycontrolled heating elements are embedded within the showerhead, whereinthe coolant loop is one of n coolant loops embedded in the showerhead,and m is not equal to n.
 19. The apparatus of claim 13, wherein thetemperature controller is communicatively coupled to the plasma powersource and wherein the feedforward control signal is based on a plasmapower input acquired from the plasma power source.
 20. The apparatus ofclaim 19, wherein the feedforward control signal is to compensate aplasma heating of the temperature-controlled component.
 21. Theapparatus of claim 19, wherein the temperature controller is to modulatea pulse width modulation duty cycle to fully open and fully close avalve through which the coolant liquid flows.
 22. A temperaturecontroller, comprising: a feedforward input to receive an indication ofa plasma power to be input to a plasma processing chamber duringexecution of a process recipe; a feedback input to receive an indicationof an actual temperature of a component to be controlled to a setpointtemperature by the temperature controller; a processor to execute atemperature control algorithm having a feedback portion that generates acontrol effort based on a difference between the actual temperaturefeedback input and the setpoint temperature; and an actuator output toprovide an actuator signal generated by the processor from thetemperature control algorithm, the actuator signal to completely stop acoolant liquid flow to the temperature-controlled component when thetemperature falls below the setpoint temperature.
 23. The temperaturecontroller as in claim 22, wherein the control algorithm furtherincludes a feedforward portion that generates a control effort based onthe plasma power feedforward input to reduce an effect of the plasmapower on a temperature of the component.
 24. The temperature controlleras in claim 23, wherein the processor is to further generate thefeedforward control effort based on a first group of gain valuesassociated with a key value pairing of a change in the plasma inputpower and a change in the setpoint temperature between the executingstep and a preceding or subsequent plasma process recipe step.
 25. Thetemperature controller as in claim 24, wherein the processor is tofurther generate the feedforward control effort based on a group oftransient gain values associated with a key value pairing of a change inthe plasma input power and a change in the setpoint temperature betweenthe executing step and a preceding or subsequent plasma process recipestep.
 26. The temperature controller as in claim 24, wherein theactuator signal is to modulate a pulse width modulation duty cycle tofully open and fully close a valve through which the coolant liquidflows, the pulse width modulation based at least in part on the firstgroup of gain values.
 27. The temperature controller as in claim 23,wherein the processor is to further modify the liquid coolant flow ratebased on a lookup table value in response to the component temperaturecrossing a threshold level when the chamber is in an idle state.